如何从此数据库架构中获取学生列表？

发布于 2024-10-31 00:46:21 字数 1055 浏览 1 评论 0原文

我有以下数据库：

学生
StudentID
姓名
姓氏成绩

GradeId
姓名
GradeInstance

GradeInstanceId
GradeId
姓名
年
StudentInstance

StudentInstanceId
GradeInstanceId
StudentInstanceId
如何

从给定成绩实例中检索学生列表？

我使用实体框架作为 ORM，那么 LINQ 查询会是什么样子？

编辑：我需要返回 Student 对象，而不是 StudentInstance 对象，因为它们不包含我需要填充 GUI 的属性。

所以这样的事情对我不起作用，除非我在这里遗漏了一些东西。

dbContext.StudentInstances.Where(s => s.GradeInstanceId == 1);

原文

I have the following database:

Student
StudentID
Name
LastName

Grade
GradeId
Name

GradeInstance
GradeInstanceId
GradeId
Name
Year

StudentInstance
StudentInstanceId
GradeInstanceId
StudentInstanceId

How can I retrieve a list of students from a given grade instance?

I'm using Entity Framework as my ORM so what would the LINQ query be like?

Edit: I need to return Student objects, not StudentInstance object because those don't contain the attributes I need to fill the GUI with.

So something like this doesn't work for me, unless I'm missing something here.

dbContext.StudentInstances.Where(s => s.GradeInstanceId == 1);

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我为君王 2024-11-07 00:46:21

from s in dbContext.Student
join si in dbContext.StudentInst on s.StudentID equals si.StudentInstanceID
join g in dbContext.Grade on si.GradeInstanceID equals g.GradeID
where g.Name = ...
select s;

from s in dbContext.Student
join si in dbContext.StudentInst on s.StudentID equals si.StudentInstanceID
join g in dbContext.Grade on si.GradeInstanceID equals g.GradeID
where g.Name = ...
select s;

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悍妇囚夫 2024-11-07 00:46:21

这应该可以帮助您开始......

    public static List<Student> GetStudents(int gradeId)
    {
        using (var context = new Entities())
        {
            List<Student> myList = (from s in dbContext.Student 
join si in dbContext.StudentInst on s.StudentID equals si.StudentInstanceID
join g in dbContext.Grade on si.GradeInstanceID equals g.GradeID
where g.GradeId = gradeId
select s).ToList();

         return myList;
        }
    }

使用稍微修改过的查询 :D

This should help you get started....

    public static List<Student> GetStudents(int gradeId)
    {
        using (var context = new Entities())
        {
            List<Student> myList = (from s in dbContext.Student 
join si in dbContext.StudentInst on s.StudentID equals si.StudentInstanceID
join g in dbContext.Grade on si.GradeInstanceID equals g.GradeID
where g.GradeId = gradeId
select s).ToList();

         return myList;
        }
    }

Using slightly modified query :D

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